Waste water treatment system by superconductive magnetic separation

ABSTRACT

An object of the invention is to provide a wastewater treatment system using a superconducting magnetic separator that can wash the magnetic filter efficiently. The system comprises in a bore of a superconducting magnet a removably built-up multiunit magnetic filter consisting of a plurality of single-unit magnetic filters. The multiunit magnetic filter has a total longitudinal length at least equal or greater than that of the superconducting magnet. During excitation of the superconducting magnet, a single-unit magnetic filter is removed from the upstream side (sewage side) of the multiunit magnetic filter by pushing in another single-unit magnetic filter from the downstream side (clean water side), and washed and returned to the downstream side again.

TECHNICAL FIELD

The invention relates to a wastewater treatment system bysuperconducting magnetic separation, and more particularly to awastewater treatment system for purifying wastewater using asolenoid-type superconducting magnetic separator.

The term “wastewater treatment” used herein also includes advanced orhigh-level purification treatment at a water purification plant, andadvanced treatment of underground water, river water, seawater or thelike. The term “wastewater” used herein means not only wastewater orwater discharged from various types of factories, experimentalfacilities, laboratories, school plants, household facilities, etc. butalso underground water, river water, seawater, water to be treated by awater purification plant or sewage treatment plant and the like, i.e.,it broadly means “water including materials to be separated”.

BACKGROUND ART

The wastewater from factories etc. includes various types of materialsto be separated from the wastewater from the viewpoints of environmentalprotection and recycling of resources. For example, wastewaterdischarged from a recycled paper manufacturing plant may include manymaterials to be separated such as dye and pigment contained in usedpaper, organic matter contained in adhesive, and coagulant added duringconventional wastewater treatment. Since these substances are causativeagents that raise COD (Chemical Oxygen Demand), the discharge of suchsubstances has been strictly regulated recently for environmentalprotection. Similarly, with reference to not only the index of COD, butalso indexes of BOD (Biochemical Oxygen Demand) and TOC (Total OrganicCarbon), the discharge of causative agents that raise these indexesshould be regulated from the viewpoint of environmental conservation.

In conventional wastewater treatment, after normal treatment usingcoagulant, biological treatment is performed using activated sludge.Specifically, organic matter contained in the wastewater is degraded bya variety of bacterium or aggregations of organisms (activated sludge)and then discharged.

The prior art documents related to the invention of the patentapplication include for example the following: Japanese PatentPublication No. 2002-292565; Japanese Patent Publication No.2002-210311; Japanese Patent Publication No. 2002-180101; JapanesePatent Publication No. 2002-292305; Japanese Patent Publication No.2002-316068; Japanese Patent Publication No. 2002-316069; and JapanesePatent Publication No. 2002-316067.

DISCLOSURE OF THE INVENTION

(Problems to be Solved by the Invention)

The conventional biological treatment using activated sludge involvesproblems that large-scale facilities and vast installation area arerequired because of slow throughput speed of the biological treatment,and that sophisticated skills are needed to control the conditions forefficiently utilizing the activated sludge.

The object of the invention is therefore to provide a wastewatertreatment system that can solve the above-mentioned problems involved inthe wastewater treatment by the activated sludge and that can achieveadvanced treatment with low cost, small space, high efficiency and highspeed.

Moreover, in a conventional general-purpose superconducting magneticseparator, in order to wash a magnetic filter, the superconductingmagnet has to be stopped for a time to backwash the magnetic filter orto remove, wash and re-mount the filter, and then the magnet must beexcited again. As the result, it is very inefficient in point of time,cost and operation.

Another object of the invention is therefore to provide a wastewatertreatment system using a superconducting magnetic separator in which amagnetic filter can be washed efficiently.

(Means for Solving the Problems)

To solve the above-mentioned problems, the invention provides awastewater treatment system, wherein magnetism is added to material tobe separated, and then the material is separated from wastewater by asolenoid-type superconducting magnet, characterized in that saidaddition of magnetism to the material to be separated is performed byattaching the material to magnetism-seeded porous material, activatedcarbon or carrier used as sorption agent.

The superconducting magnetic separator used in the wastewater treatmentsystem according to the invention may comprises in a bore of thesuperconducting magnet a removably built-up multiunit (or multistage)magnetic filter consisting of a plurality of single-unit magneticfilters, the multiunit magnetic filter having the total longitudinallength at least equal or greater than that of the superconductingmagnet. Such structure leads to an advantage that it is possible toremove a single-unit magnetic filter from the upstream side (sewageside) of the multiunit magnetic filter by pushing in another single-unitmagnetic filter from the downstream side (clean water side), and to washand return the removed filter to the downstream side again even duringexcitation of the superconducting magnet.

The system may be configured in such a way that magnetism is added tothe material to be separated in wastewater by attaching the material toa magnetic sorption agent in a treatment tank under the action ofsorption, and that the magnetic filters are washed in the same treatmenttank, so that the sorption agent attached to the magnetic filters can byreleased and returned directly to the treatment tank. In suchconfiguration, microorganism-adhered carrier such as biologicalactivated carbon may also be used as sorption agent. Such purificationof wastewater by biodegradation using microorganism-adhered carrier isalso referred to as “wastewater treatment by microorganismimmobilization method”.

Moreover, the superconducting magnetic separator used in the wastewatertreatment system according to the invention may comprise a pair ofmagnetic filters connected to each other and movable in a longitudinaldirection through the bore of the superconducting magnet in order toswitch the magnetic filter for alternate use, so that while one magneticfilter is used for magnetic separation in the bore, the other magneticfilter can be backwashed outside the bore.

(Advantages of the Invention)

Thanks to the embodiment of the wastewater treatment system comprising amagnetism adding means for adding magnetism to material to be separated,and a solenoid-type superconducting magnetic separation means forcollecting and separating the magnetism-added material by the magneticfield generated by the solenoid-type superconducting magnet,characterized in that said magnetism adding means adds magnetism to thematerial to be separated by attaching the material to magnetism-seededporous material, activated carbon or carrier used as sorption agent,many advantages are gained such as very low cost of facilities, smallspace, simple operationality, high speed treatment, high efficiency, andadvanced treatment, compared to the prior art. Additionally, themagnetic sorption agent can be recovered, regenerated and reused, whichimproves the efficiency and cost performance of the system.

Moreover, the removably built-up multiunit magnetic filter consisting ofa plurality of single-unit magnetic filters is provided in a bore of thesuperconducting magnet and the multiunit magnetic filter has thelongitudinal length at least equal or greater than that of thesuperconducting magnet; so that it is easy to remove sequentiallysingle-unit magnetic filters from the upstream side by pushing in cleansingle-unit magnetic filters in sequence from the downstream side, andto wash and return the removed single-unit filters to the downstreamside, without reducing the magnetic field even during excitation of thesuperconducting magnet.

More detailed explanation on its operational principle is given below.Essentially, it is the most stable condition that the longitudinalcenter of the multiunit magnetic filter is positioned at thelongitudinal center of the magnetic field generated by thesuperconducting magnet. Accordingly, if the multiunit magnetic filter insuch most stable condition is made to be moved slightly longitudinally,it is strongly pulled back to the center of the magnetic field. Even inthis condition, if one single-unit magnetic filter is pushed in from thedownstream side, the multiunit magnetic filter is lengthened at thedownstream side and the longitudinal center of the multiunit filter isshifted towards the downstream side; thus, pulling force is generated topull the filter towards the upstream side for achieving more stablecondition. As the result, a single-unit magnetic filter is pushed outtowards the upstream side, which makes it easy to remove it from themultiunit magnetic filter.

Moreover, according to another embodiment, single-unit magnetic filtersremoved from the upstream side of the multiunit magnetic filter arewashed by an ultrasonic cleaning apparatus or the like in the treatmenttank so as to return the magnetic sorption agent directly to thetreatment tank; thus, the sorption agent can be efficiently recovered,regenerated and reused.

Furthermore, according to another embodiment, microorganism-adheredmagnetic carrier such as biological activated carbon is used as sorptionagent and is kept in the tank without taking out sludge to the outsideof the tank, so that both the functions of adsorption and biodegradationcan be utilized. Thus, higher speed and advanced treatment is achievedat high efficiency and low cost. Further, the microorganisms attached tothe surface of the biological activated carbon also degrade the organicmatter with which the pores on the surface of the activated carbon areclogged, and regenerate the performance of adsorption or absorption ofthe activated carbon. Thus, the frequency of replacement of theactivated carbon can be reduced.

Moreover, according to another embodiment of the system configured insuch a way that a pair of magnetic filters connected to each other andmovable longitudinally is disposed in a bore of a superconducting magnetso that while one magnetic filter is positioned in the bore forwastewater treatment, the other magnetic filter may be backwashedoutside the bore (switchback type), the wastewater treatment can beperformed without time loss required for switching the magnetic filter,and it is unnecessary to provide a mechanism for removing a single-unitmagnetic filter from the upstream side, washing and returning it to thedownstream side. Further, the switchback-type magnetic filter isdisposed in a closed container; thus, even if bacterium such asEscherichia coli 0157 and/or toxic substances such as endocrinedisrupting chemicals are captured, it is possible to perform necessarytreatment in the tank and take out them without spreading.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below with reference to the drawings:

FIG. 1 is a schematic illustration of a wastewater treatment systemaccording to the invention;

FIG. 2 is a schematic illustration of another embodiment of a wastewatertreatment system according to the invention;

FIG. 3 shows the results of a removable test for substances causing therise of COD, the test having done by the wastewater treatment systemaccording to the invention;

FIG. 4 is a schematic illustration of a multiunit magnetic filter and atransfer and wash apparatus for single-unit magnetic filters, used inthe wastewater treatment system according to the invention;

FIG. 5 is a schematic illustration of a single-unit magnetic filter,where FIG. 5(a) is a front view and FIG. 5(b) is a sectional view takenalong line B-B′ in FIG. 5(a);

FIG. 6 illustrates the configuration of another embodiment according tothe invention, in which sorption agent attached to single-unit magneticfilters are released by an ultrasonic cleaning apparatus in a treatmenttank and returned directly to the tank;

FIG. 7 is a schematic illustration of a switchback-type superconductingmagnetic separator according to the invention; and

FIG. 8 is an illustration of the experiment of magnetic separation whichwas carried out using a multiunit magnetic filter according to theinvention, wherein the used multiunit magnetic filter is composed of 13magnetic filter cassettes (FIG. 8(a)), and each magnetic filter cassetteis a built-up one made of 4 magnetic filters (FIG. 8(b)).

BEST MODE FOR CARRYING OUT THE INVENTION

The wastewater treatment system according to the invention comprises amagnetism adding means for adding magnetism to material to be separated,and a superconducting magnetic separation means for separating thematerial from wastewater by collecting the magnetism-added material bythe magnetic field generated by a solenoid-type superconducting magnet.

Only the magnetism-added material to be separated in wastewater flowingaxially in a solenoid-type superconducting magnet may be attached to thewall in the magnet bore by magnetic field generated by thesuperconducting magnet. Such magnetic separator using an air-coresolenoidal magnet with no magnetic material disposed in the magneticfield is also referred to as “open-type filter system”.

The wastewater treated by the invention includes but not limited to thewastewater from various factories such as paper mill, food productsfactory, semiconductor factory, chemical products factory, dye works,plating factory. For example, wastewater made in daily life, wastewaterdischarged from a school plant or laboratory, etc. may also be treated.The term “wastewater” used in the specification may also include, forexample, river water, underground water, etc. Such wastewater iscollected and purified by a sewage treatment plant or water purificationplant. Thus, the purification treatment by the water purification plantis also included in the “wastewater treatment” used in thespecification.

The material to be separated from wastewater may includes a variety ofmaterials, for example, dye, pigment, adhesive, cellulose, coagulant,etc. (substances causing the rise of COD) contained in the wastewaterdischarged from a paper mill, recycled paper manufacturing plant, etc.,inorganic substances such as SiC and SiO₂ contained in waste fluiddischarged from a semiconductor factory, nonmagnetic substancesincluding biological material such as blue-green algae, heavy oil, metalion and the like. These materials are solely cited as an example, andshould not be limited thereto. The material to be separated may alsoinclude, for example, Escherichia coli 0157, endocrine disruptingchemicals and the like.

The addition of magnetism (or magnetization) to the material to beseparated (referred to as “magnetic seeding”) may be performed by, forexample, a colloid chemical magnetic seeding method, a mechanochemicalmagnetic seeding method, an electrochemical magnetic seeding method,etc. In the colloid chemical magnetic seeding method, for example,colloid of iron oxide is attached to the material to be separated byol-dization or oxo-dization, or the material to be separated is oxidizedby precipitation or coprecipitation of iron hydroxide. In themechanochemical magnetic seeding method, magnetic substance such as ironchip is mechanically attached to the material to be separated.

Alternatively, magnetism may be seeded to the sorption agent in advanceby a colloid chemical magnetic seeding method, a mechanochemicalmagnetic seeding method, an electrochemical magnetic seeding method orthe like, and then magnetism may be added to the material to beseparated, by sorption (i.e. adsorption and/or absorption) of thematerial to the sorption agent. The sorption agent may includemagnetite, ceramic porous material, zeolite porous material, activatedcarbon, plastic carrier, etc. Making sorption agent as porous materialleads to high efficiency of adsorption and/or absorption.

The superconducting magnetic separation means according to the inventionmay be configured in such a way that magnetic fine wires are disposed inthe magnetic field to generate high gradient magnetic field (closedfilter type). The magnetism-added material in wastewater is attached tothe magnetic fine wires under the action of this high gradient magneticfield. In this manner, the magnetic fine wires disposed in the magneticfield make it possible to generate high gradient magnetic field, so thatmagnetic force acting on the material to be separated is enhanced toachieve more efficient treatment.

A sedimentation tank may be disposed between the magnetism adding meansand the magnetic separation means to separate the sedimentary materialfrom the wastewater, which improves the efficiency of separation.

According to another embodiment of closed filter type, the invention maycomprises a removably built-up multiunit magnetic filter consisting of aplurality of magnetic filters (“single-unit magnetic filters”) made ofmagnetic material such as magnetic fine wires, the multiunit magneticfilter being disposed in a bore of a superconducting magnet, and havingthe longitudinal length at least equal or greater than that of thesuperconducting magnet. Such structure leads to the advantage that it iseasy to remove sequentially the single-unit magnetic filters at anupstream side where more material to be separated is captured, bypushing in clean single-unit magnetic filters one by one from adownstream side, and to wash and return the removed filters to thedownstream side again, even during excitation of the superconductingmagnet (i.e. during generation of magnetic field). This operationalprinciple is described above. This enables continuous treatment withoutinterrupting the magnetic separating treatment for washing thesingle-unit magnetic filters.

In conventional superconducting magnetic separation, in order to removethe material captured in the magnet, the excited superconducting magnetmust be stopped for a time to remove the material, and then be exitedagain; thus, its efficiency is very low. This is because magneticfilters are strongly held at the center of the magnetic field generatedby the superconducting electromagnet during operation of the magnet, sothat it is hard to take out the magnetic filters to the outside of thebore of the magnet during its excitation. For this reason, thesuperconducting magnet has to be stopped for a time to remove, wash andre-mount the magnetic filters, or to backwash the filters disposed inthe magnet bore. This shortcoming is overcome by the arrangement of theinvention.

The wastewater treatment system according to the invention may furthercomprise a transfer and wash means configured in such a way that, duringexcitation of the superconducting magnet, single-unit magnetic filterscan be sequentially removed from the upstream side of the multiunitfilter by pushing in clean single-unit magnetic filters in sequence fromthe downstream side of the multiunit filter, and be washed and pushed infrom the downstream side again. To wash, any washing method mayoptionally adopted such as a suction cleaning method of sucking thematerial attached to the surface of the filter by air suction, a jetwashing method of washing the filter by pressurized water, an ultrasoniccleaning method, a bubble cleaning method, and any combination thereof.

Preferably, the transfer and wash means may be configured in such a waythat an ultrasonic cleaning apparatus is provided in a treatment tank,the single-unit magnetic filters removed from the upstream side of themultiunit magnetic filter are transferred to the cleaning apparatus inthe treatment tank, and attached sorption agent is released and returneddirectly to the treatment tank. Since the sorption agent such asactivated carbon, ceramic porous material, and ceramic or plasticcarrier is returned directly to the treatment tank, the sorption agentcan be efficiently recovered, regenerated and reused.

In the embodiment where the sorption agent is returned directly to thetreatment tank, it is also possible to use microorganism-attachedcarrier as sorption agent, for example, activated carbon having asurface on which microorganisms are attached (i.e. biological activatedcarbon). The biological activated carbon has a function ofbiodegradation as well as a function of adsorption or absorption of thematerial to be separated; hence, organic matter is degraded in thetreatment tank, which improves the performance of clarification with thehelp of magnetic separation. Additionally, the organic matter with whichthe pores on the surface of the activated carbon are clogged is degradedby the function of biodegradation of the biological activated carbon toregenerate the activated carbon; thus, the frequency of replacement ofthe activated carbon can be reduced.

According to another embodiment, instead of the multiunit magneticfilter, a pair of magnetic filters connected to each other and movablein a longitudinal direction through the bore of the superconductingmagnet may be utilized for alternate use in such a way that while onemagnetic filter is used for wastewater treatment in the bore of themagnet, the other magnetic filter can be backwashed outside the bore(referred to as “switchback type”). Such structure leads to advantagesthat the wastewater treatment can be performed efficiently without anyloss of time, and that it is not required to provide a transfer and washmeans for removing single-unit magnetic filters from the upstream sideand for washing and returning them to the downstream side. Further, theswitchback-type magnetic filter is disposed in a closed container. Thus,even if bacterium such as Escherichia coli 0157, toxic substances suchas endocrine disrupting chemicals, etc. are captured, it is possible totake out them after necessary treatment without spreading; hence, highsafety can be achieved.

Embodiments

Embodiments of the invention will be described below with reference tothe drawings.

FIG. 1 is a schematic illustration of an embodiment of a wastewatertreatment system according to the invention. First, wastewater 1discharged from a factory or the like is passed to a magnetism-adding(or magnetizing or magnetic seeding) apparatus 2 through a filter 6. Inthe magnetism-adding apparatus 2, magnetism is added to dye, pigment,organic matter contained in adhesive, etc. (i.e. materials to beseparated) by attaching them to magnetic sorption agent 5 in thewastewater under the action of sorption during stir. Alternatively, inthe magnetism-adding apparatus 2, magnetism may be added or seededdirectly to the material by a colloid chemical magnetic seeding methodor a mechanochemical magnetic seeding method instead of use of thesorption agent 5.

The wastewater containing the magnetism-added or magnetism-seededmaterial to be separated is transferred to a superconducting magneticseparator 3, and is passed through the high-strength and high-gradientmagnetic field generated by a solenoid-type superconducting magnet. Inthe case of an open-type filter system having no magnetic fine wiresdisposed in the magnetic field of the solenoid-type magnet, themagnetism-added material is attached to the pipe wall in the magnetbore. In the case of a closed-type filter system having magnetic finewires disposed in the magnetic field, the magnetism-added material isattached to the magnetic fine wires. From the material 4 thus separated,the magnetic sorption agent 5 is recovered, regenerated and reused,while the remains are discarded. The separated water is discharged intoa sewer or recycled.

FIG. 2 shows another embodiment of the invention. The embodiment differsfrom that of FIG. 1 in that-an additional sedimentation tank 7 isdisposed between the magnetism-adding apparatus 2 and the magneticseparator 3. In the sedimentation tank 7, the material to be separatedis separated from water by sedimentation of the material.

FIG. 3 shows the results of a removal test for substances causing therise of COD in wastewater. The test was done by the wastewater treatmentsystem according to the invention. The concentration of the substancescausing the rise of COD in the raw wastewater was about 150 mg/l. Afterthe first separation by a pre-filter (indicated by 6 in FIG. 1), theconcentration was about 70 mg/l. After the second separation by thesedimentation tank (indicated by 7 in FIG. 2) after addition ofmagnetism, the concentration was about 40 mg/l. And after magneticseparation (indicated by 3 in FIG. 2), the concentration was about 20mg/l. Thus, these results indicate good performance of removal by thewastewater treatment system according to the invention.

FIG. 4 illustrates the multiunit magnetic filter 31 used in thewastewater treatment system according to the invention, and the mannerof washing the single-unit magnetic filters 32 making up the multiunitmagnetic filter 31. The multiunit magnetic filter 31 is a removablybuilt-up filter that is composed of a plurality of single-unit magneticfilters 32. The longitudinal length of the multiunit magnetic filter isat least equal or greater than that of the superconducting magnet 30. Asdescribed in detail below, as the position of the single-unit magneticfilter approaches the upstream side (wastewater inflow side), thematerial to be separated is more captured in the multiunit magneticfilter 31. Thus, preferably, single-unit magnetic filters 32 aresequentially removed from the upstream side by pushing in othersingle-unit magnetic filters 32 in sequence from the downstream side,and are washed and returned to the downstream side. When the single-unitmagnetic filter 32 is removed from the upstream side, it is pushed up,for example, in the direction perpendicular to the longitudinaldirection of the magnet. For washing, any washing method may beoptionally used such as bubble cleaning, ultrasonic cleaning, jetcleaning, suction cleaning and any combination thereof.

The multiunit magnetic filter 31 has a whole longitudinal length atleast equal or greater than that of the superconducting magnet 30, whichmakes it easy to sequentially take out the single-unit magnetic filters32 from the upstream side by pushing in other single-unit magneticfilters 32 one by one from the downstream side, and to return them tothe downstream side after-washing even during excitation of thesuperconducting magnet 30. This is based on the nature that the moststable condition is achieved when the longitudinal center of themultiunit magnetic filter is positioned at the longitudinal center ofthe magnetic field of the superconducting magnet. Specifically, when onesingle-unit magnetic filter is pushed in from the downstream side, thelength of the multiunit magnetic filter is extended towards thedownstream side and the longitudinal center is shifted towards thedownstream side; thus, the multiunit magnetic filter is pulled towardsthe upstream side for more stable condition. As the result, asingle-unit magnetic filter is pushed out at the upstream side, whichmakes it easy to remove it from the multiunit magnetic filter.

FIG. 5 illustrates as an example one single-unit magnetic filter 32 ofthe multiunit magnetic filter 31. A wire netting 34 made of magneticmaterial is set to a filter case 50, and it is supported by supports 35if necessary. The mesh size of the wire netting 34, the diameter andthickness of the filter may be optionally determined based on theprocessing object and processing power. The wire netting may beremovably set, and/or set in a pile.

Magnetic force is applied to magnetic material such as wire netting 34to force it to be arranged along the direction of the magnetic fieldline in the magnetic field. As the result, if one single-unit magneticfilter is placed in the bore of a solenoidal magnet, it will be forcedto be laid along the axial direction. Thus, if there is any spacebetween the continuously built-up single-unit magnetic filters 32, thesingle-unit magnetic filters are forced to be laid, which involves therisk of preventing the close multiunit formation. In order to avoidthis, preferably, the axial stability is enhanced by using the filtercase 50 made of magnetic material or by fixing proper number of axialrods of magnetic material to the filter case 50 in place.

With reference to FIG. 6, in the wastewater treatment system using themultiunit magnetic filter 31 according to the invention, the sorptionagent 37 such as activated carbon and porous material is released in thetreatment tank 51 from the single-unit magnetic filters 32 by anultrasonic cleaning apparatus 36 and returned directly into the tank(referred to as “sorption agent holding type magnetic filter system”).Since the sorption agent 37 is returned directly to the treatment tank51, it is easy to recover the sorption agent 37 deposited on the bottomof the treatment tank 51, for example, and to regenerate and reuse them.

In such structure, in case biological activated carbon is used assorption agent, it is possible to utilize the both of the functions ofadsorption carried out by the activated carbon and of biodegradationcarried out by microorganism layer formed on the surfaces of theactivated carbon particles to purify the water. Thus, organic matter canbe removed efficiently by a small amount of activated carbon. Theorganic matter with which the pores on the surface of the activatedcarbon are clogged is also subjected to biodegradation to regenerate theactivated carbon; thus, the frequency of replacement of the activatedcarbon can be reduced (for example one time every three years). In suchtreatment method, the magnetic separation using the multiunit magneticfilter according to the invention is combined with the biodegradationprocess by biological activated carbon (referred to as “magneticseparation type biological activated carbon treatment method”).

On the other hand, in a conventional biological activated carbontreatment method, throughput speed (flow rate) cannot be raised muchbecause it is required to prevent the effluence of activated carbon fromthe biological treatment tank. On the contrary, in the magneticseparation type biological activated carbon treatment method accordingto the invention, the magnetic separator is placed at an outlet ofpurified water from the biological treatment tank; thus, such structureleads to a processing power with a flow rate of about 10-20 cm/s. Thecapacity of the treatment tank may be determined in such a way that thedwell time of water in the treatment tank is about 10 minutes.Accordingly, the magnetic separation type biological activated carbontreatment method according to the invention may lead to very highprocessing speed, reduced size of a system (one tenths relative to aconventional system for example), and low cost relative to aconventional biological activated carbon treatment method.

FIG. 7 illustrates a switchback-type magnetic separator according to theinvention. The nonmagnetic or weakly magnetic tubular container 39 ispartitioned at the center into two chambers 44 and 45 by a partitionplate 43. Each chamber 44, 45 is divided into a forward passage section40 and a backward passage section 41 by a separating wall 42. Eachforward passage section 40 is provided with a magnetic filter 38. As themagnetic filter 38, it is possible to optionally adopt a built-up typemultiunit magnetic filter composed of a plurality of single-unitmagnetic filters, an integrated-type magnetic filter or the like. Theentire tubular container 39 can be moved in the longitudinal directionindicated by an arrow A in a bore of the superconducting magnet 30 byany suitable driving means (not shown). Each chamber 44, 45 is providedwith an inlet of raw wastewater and an outlet of treated wastewater. Thewastewater from the inlet is passed through the magnetic filter 38disposed in the forward passage section 40 for filtration, and is passedthrough the backward passage section 41 to discharge it from the outlet.By proper operation of valves (not shown), the inflow of the rawwastewater into one chamber can be stopped so as to enable the inflowinto the other chamber. After moving one chamber to the outside of themagnetic field, proper operation of valves (not shown) makes it possibleto feed cleaning water from the outlet through the backward passagesection 41 to the forward passage section 40 for backwashing themagnetic filter 38, and to discharge sludge-containing water from theinlet after washing. Bubbling air supply pipes are provided near themagnetic filter 38 for enhancing washing power.

In the case of such switchback-type magnetic separator, if it isrequired to wash one magnetic filter in use, the container 39 housingthe magnetic filter is moved by a driving means to pull the magneticfilter out of the superconducting magnet 30 for backwashing, and toposition the other magnetic filter in the bore of the superconductingmagnet for filtration. During the filtration, the magnetic filter thathas been used is backwashed. In this way, the magnetic filter may beswitched for alternate use in such a manner that while one magneticfilter is used for filtration, the other magnetic filter can be washed;thus, it is highly efficient. Further, the magnetic filters inthemselves are disposed in the closed container, so that even when thefilter captures bacterium such as Escherichia coli 0157 or toxicsubstances such as endocrine disrupting chemicals, it is possible totake out them after necessary treatment.

FIG. 8 illustrates the configuration of the experiments of magneticseparation that were carried out by the multiunit magnetic filteraccording to the invention. As shown in FIG. 8(a), the built-upmultiunit magnetic filter 31 is composed of 13 magnetic filter cassettes46 (indicated by (1), (2) . . . (13) respectively from the inflow side).As shown in FIG. 8(b), each magnetic filter cassette 46 is composed of 4magnetic filters 47, and spacers 48 having a width of 1 cm are disposedbetween respective magnetic filters 47.

(Experiment 1)

The magnetic field of 3 T was generated by the superconducting magnet30, and water of 10 liters to which magnetite (“ISETITE”) of 50 g wasadded (i.e. the concentration of 5% by weight) was passed through fromthe upstream side at a flow rate of 800 ton/day (i.e. 8 cm/s) forfiltration. After the filtration, the magnetic field was reduced forcarefully removing the magnetic filter cassettes, and the amount of themagnetite attached to the respective cassettes was measured. The resultsare shown in TABLE 1. As seen from TABLE 1, more amount of magnetite wascaptured by a magnetic filter cassette positioned at nearer to theupstream side, and about 70% of the magnetite was recovered by thecassettes (1) and (2). TABLE 1 Cassette No. Captured magnetite (g)Percentage (%) (1) 18.3456 36.7 (2) 17.4468 34.9 (3) 3.2045 6.4 (4)1.3614 2.7 (5) 0.6354 1.3 (6) 0.3211 0.6 (7) 0.1432 0.3 (8) 0.0933 0.2(9) 0.0710 0.1 (10)  0.0530 0.1 (11)  0.0359 0.1 (12)  0.0204 0.0 (13) 0 0.0 total 41.7599 83.5(Experiment 2)

Similarly to the experiment 1, the magnetic field of 3 T was generatedby the superconducting magnet, and magnetite-containing water was passedthrough for filtration. After filtration, without reducing the magneticfield, a total of 7 cassettes were pushed in one by one from thedownstream side to sequentially take out the cassettes (1)-(7) from theupstream side, and the amount of magnetite was measured. The results areshown in TABLE 2. As seen from TABLE 2, the amounts of magnetitecaptured by the cassettes (1)-(7) are approximately the same as those ofthe experiment 1, and about 70% of the magnetite could be recovered bythe cassettes (1) and (2) positioned at the upstream side. Thisindicates that even during excitation of the superconducting magnet, themagnetite attached to the magnetic cassettes can be successfullyseparated and removed without attachment of the magnetite to thesuperconducting magnet. TABLE 2 Cassette No. Captured magnetite (g)Percentage (%) (1) 18.8518 37.7 (2) 18.5678 37.1 (3) 3.1032 6.2 (4)1.3784 2.8 (5) 0.6388 1.3 (6) 0.2903 0.6 (7) 0.1609 0.3 total 42.991286.0

1. A wastewater treatment system comprising a magnetism adding means foradding magnetism to material to be separated in wastewater, and asuperconducting magnetic separation means for separating the materialfrom the wastewater by collecting the magnetism-added material throughthe magnetic field generated by a solenoid-type superconducting magnet,characterized in that: said magnetism adding means adds magnetism to thematerial by attaching the material to magnetism-seeded porous material,activated carbon or carrier used as a sorption agent.
 2. A wastewatertreatment system comprising a magnetism adding means for addingmagnetism to material to be separated in wastewater, and asuperconducting magnetic separation means for separating the materialfrom the wastewater by collecting the magnetism-added material throughthe magnetic field generated by a solenoid-type superconducting magnet,characterized in that: said superconducting magnetic separation meanscomprises in a bore of the superconducting magnet a removably built-upmultiunit magnetic filter consisting of a plurality of single-unitmagnetic filters, and the multiunit magnetic filter has the longitudinallength at least equal or greater than that of the superconductingmagnet.
 3. The wastewater treatment system as claimed in claim 2,characterized in that the system further comprises a transfer and washmeans for removing a single-unit magnetic filter from an upstream side(sewage side) of said multiunit magnetic filter by pushing in anothersingle-unit magnetic filter from a downstream side (clean water side),and for washing and returning the removed filter to the downstream sideagain during excitation of the superconducting magnet.
 4. The wastewatertreatment system as claimed in claim 3, characterized in that: saidmagnetism adding means adds magnetism to the material to be separated byattaching the material in the wastewater to the magnetism-seededsorption agent in a treatment tank, and said washing of the single-unitmagnetic filters is performed in the treatment tank so that the sorptionagent attached to the single-unit magnetic filters may be released andreturned directly to the treatment tank.
 5. The wastewater treatmentsystem as claimed in claim 4, based on a microorganism immobilizationmethod, characterized in that said sorption agent is amicroorganism-adhered carrier.
 6. A wastewater treatment systemcomprising a means for adding magnetism to material to be separated inwastewater, and a superconducting magnetic separation means forseparating the material from the wastewater by collecting themagnetism-added material through the magnetic field generated by asolenoid-type superconducting magnet, characterized in that: saidsuperconducting magnetic separation means comprises a pair of magneticfilters connected to each other and movable in a longitudinal directionthrough a bore of the superconducting magnet, the movement enabling theswitching of the magnetic filter for alternate use in such a way thatwhile one magnetic filter is used for wastewater treatment in the boreof the magnet, the other magnetic filter can be backwashed outside thebore.